The team synthesized the chromosome of a modified Mycoplasma mycoides genome, which consists of 1.08 million base pairs.

The synthetic cell is called Mycoplasma mycoides JCVI-syn1.0 and proves that genomes can be designed on a computer, chemically constructed in a laboratory and transplanted into a recipient cell to produce a new, self-replicating cell controlled only by the synthetic genome.

"This is as much a philosophical advance as a scientific one," founder J. Craig Ventersaid at the press conference. "It's a giant philosophical change in how we view life."

Pros

The ability to write genetic code.

Better understand the fundamentals of living cells.

Develop more effective pharmaceuticals, such as a vaccine for HIV.

Advance water-cleaning functions, or efficient new biofuels that work at scale.

Develop improved genetically-altered food.

A "progressive increase" in research capability, Venter said.

Cons

It's possible to use this knowledge to synthesize a pathogen. A "linear increase" in danger here, Venter said.

Screening procedures will be needed for those who want to order 1000-base pair pieces of DNA to detect malicious intent.

Raises questions about the ability to patent life.

"It's not building life from scratch," Venter said, adding that it took his team 15 years to accomplish the feat. "Like any life on Earth, we're creating new life from existing life."

Scientists began the process with the accurate, digitized genome of the bacterium M. mycoides. The team designed 1,078 specific "cassettes" of DNA that were 1,080 base pairs long. Made to JCVI specifications by DNA synthesis company Blue Heron Biotechnology, the cassettes were designed so that the ends of each DNA cassette overlapped each of its neighbors slightly.

The team used a three-stage process that utilized the team's yeast assembly system to build out the genome from the 1,078 cassettes. It then took the resulting, lengthened segments and assembled them into the complete synthetic genome in yeast cells.

The complete synthetic genome was isolated from the yeast cell and transplanted into recipient Mycoplasma capricolum cells that had the genes for its restriction enzyme removed.

The synthetic genome DNA was transcribed into messenger RNA, which in turn was translated into new proteins. (The original genome was either destroyed by the synthetic genome's restriction enzymes or was lost during cell replication.)

After two days, viable M. mycoides cells with synthetic DNA were created.

Encountering difficulty producing viable cells, the team developed an error correction method to test that each cassette constructed was biologically sound. DNA sequencing revealed that a single base pair deletion in an essential gene was responsible; once corrected, the team produced the first viable synthetic cell.

"If you purchase a computer at a store, it doesn't do anything unless you install an operating system on it," said Hamilton Smith, JCVI's director of synthetic biology and bioenergy. "We're in effect designing the software and installing it into a cytoplasm. The cell then does what we have designed it to do."

"It's designed to be biologically neutral," another executive added.

The research was funded by Synthetic Genomics for eventual intellectual property rights. The firm has a contract from oil giant Exxon to generate biofuels from algae.

It will be published in the May 20 edition of Science Express and Science.